Methods for quenching metal tubes

ABSTRACT

Improved methods for quenching a metal tube are disclosed. A method of manufacturing a metal tube generally comprises solution heat treating a metal tube at an elevated temperature, rapidly cooling the metal tube from the elevated temperature, raising the open end of the metal tube to an elevated position, and lowering the open end of the metal tube to a downward facing position, wherein the metal tube comprises an open end and an opposing closed end, wherein the immersing step comprises at least partially filling the metal tube with the cooling liquid, and developing an evolved gas inside the metal tube, wherein the raising comprises releasing at least some of the evolved gas from the metal tube via the open end, and wherein the lowering comprises draining cooling liquid from the metal tube via the open end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims benefit of priority of U.S. Provisional Patent Application No. 62/308,350, filed Mar. 15, 2016, and United Kingdom Patent Application No. 1605552.7, filed Apr. 1, 2016, both entitled “IMPROVED METHODS FOR QUENCHING METAL TUBES”, each of which is incorporated herein by reference in its entirety.

BACKGROUND

Many different metals can be made into alloys, such as aluminum, nickel, titanium, cobalt or steel. These alloys may be thermally modified to yield improved properties. It is often difficult to improve one property of an alloy without degrading another property.

SUMMARY OF THE DISCLOSURE

Broadly, the present patent application relates to an improved process for quenching closed end metal tubes during their manufacture to facilitate consistent and more uniform cooling. For instance, a method may comprise heat treating a metal tube at an elevated temperature, and, after the heat treating step, rapidly cooling the metal tube from the elevated temperature. The metal tube comprises one open end and one closed end opposite the open end. The rapidly cooling of the metal tube may include the sequential steps of immersing the metal tube in a cooling liquid, raising the open end of the metal tube to an elevated position, and lowering the open end of the metal tube to a downward facing position. The immersing step may include at least partially filling the metal tube with the cooling liquid, which may result in the development of an evolved gas inside the metal tube. The raising step may comprise releasing at least some of the evolved gas from the metal tube via the open end. The lowering step may comprise draining cooling liquid from the metal tube via the open end.

In some embodiments, the metal tube may be an extruded metal tube. In some embodiments, the metal tube may be a machined metal tube, a casted metal tube, a hogged metal tube, or a metal tube fabricated from multiple parts. In some embodiments, the elevated temperature is sufficient to place soluble constituents of the metal into a solid solution and/or to affect or prevent a phase change in the metal. In some embodiments, the metal tube may comprise a nickel alloy, a cobalt alloy, a steel alloy, an aluminum alloy or a titanium alloy.

In some embodiments, the rapidly cooling step comprises a quenching step, wherein the cooling liquid is a quenching liquid. In some embodiments, the quenching liquid may be an aqueous liquid or an organic liquid or a combination of an aqueous and organic liquid. The aqueous liquid may be water, water plus carbon dioxide, or water plus a polymer. The organic liquid may comprise an oil or an organic aqueous polymer.

In some embodiments, the immersing step comprises (A) fully submerging the metal tube in the cooling liquid, and (B) developing an evolved gas inside the metal tube. In another aspect, the immersing step comprises (A) positioning the metal tube in a substantially horizontal position, (B) at least partially filling the metal tube with the cooling liquid, and (C) developing an evolved gas inside the metal tube. In other embodiments, the immersing step comprises (A) positioning the metal tube in a substantially horizontal position, (B) submerging the metal tube in the cooling liquid, and (C) developing an evolved gas inside the metal tube.

In some embodiments, the raising step further comprises removing the metal tube fully from the cooling liquid. In some embodiments, the raising step comprises tilting the metal tube such that the open end of the metal tube faces upward by an angle of from 1 to 45 degrees above the horizontal axis, and wherein lowering step comprises tilting the metal tube such that the open end of the metal tube faces downward by an angle of from 1 to 45 degrees below the horizontal axis. In some embodiments the raising step further comprises removing the metal tube fully from the cooling liquid.

In some embodiments, the positioning step comprises positioning the metal tube in a substantially horizontal position on a tiltable device. The tiltable device may a quenching table or may be the bed of a furnace.

In another aspect of the present disclosure, disclosed is a method of manufacturing a metal tube comprising (a) heat treating an extruded metal tube at an elevated temperature, wherein the metal tube comprises an open end and an opposing closed end, and after the heat treating step, (b) quenching the metal tube. The quenching comprises (i) positioning the metal tube on a tiltable device, (ii) immersing the metal tube in a quenching liquid, (iii) raising, with the tiltable device, the open end of the metal tube to an elevated position, (iv) removing the metal tube and the tiltable device from the quenching fluid, and (v) lowering, with the tiltable device, the open end of the metal tube to a downward facing position, wherein the lowering comprises draining cooling liquid from the metal tube via the open end. The raising step further comprises releasing at least some of the evolved gas from the metal tube via the open end. The immersing step comprises (A) at least partially filling the metal tube with the quenching liquid, and (B) developing an evolved gas inside the metal tube.

Other related embodiments are as shown in the detailed description below, and in the appended claims.

Definitions

As used herein, a “metal tube” refers to a hollow, tubular product that is long in relation to its cross section. The metal tube may comprise any heat treatable metal alloy (e.g., a nickel alloy, a cobalt alloy, a steel alloy, an aluminum alloy or a titanium alloy). The metal tube may be any geometric shape, for example, it may be round, hexagonal, octagonal, elliptical, square or rectangular, with sharp or rounded corners. In some embodiments, the metal tube may have one end open and one end closed. The metal tube may be formed using any commercial forming process. For example, in one embodiment, the metal tube is monolithic. The monolithic metal tube may be a shape casted tube (e.g. a tube made via a casting process), a wrought metal tube (e.g. a tube that is first shaped via a process such as extrusion, or a tube which is extruded and then drawn), or a machined tube (e.g., a tube hogged from a solid bar of metal). In some embodiments, the metal tube may comprise one or more physical structures (e.g., ribs, lugs or flanges) formed with a die during an extrusion process, the structures being formed onto an outside or inside surface of the metal tube. In another embodiment, the metal tube is a multipiece metal tube. The multipiece metal tube may be a tube fabricated from multiple parts. In some embodiments, a cap or end may be welded or attached to a hollow tube with both ends open to yield a fabricated metal tube having one open end.

As used herein, “substantially horizontal position” shall mean the metal tube is positioned on a surface such that its horizontal axis is substantially horizontal. “Substantially horizontal” shall mean the horizontal axis is at an angle of from 0 to about 15 degrees above or below horizontal. In some embodiments, substantially horizontal shall mean the metal tube is positioned at an angle of not more than 10 degrees above or below horizontal. As used herein, “horizontal axis” shall mean a longitudinal axis of the metal pipe extending from one end to the other end.

As used herein, “cooling liquid” refers to any appropriate liquid for rapidly cooling metal products after a heat treatment. The cooling liquid may be a quenching liquid, which may be an aqueous liquid, an organic liquid or a combination of both aqueous and organic liquids.

As used herein, “submerging” shall mean lowering the metal tube until it is fully submerged within and filled with the cooling liquid. “Immersing” shall mean lowering at least a part of the metal tube within the cooling liquid.

As used herein, an “evolved gas” is any gas and/or vapor that develops as a result of immersing or submerging the metal tube in the cooling liquid.

As used herein, a “tiltable device” refers to any device with a surface configured to stably retain a metal tube, wherein the surface and/or the device may tilt, rotate, rock or move in a manner such that the metal tube can be positioned in and transitioned through a substantially horizontal position, an elevated position, and a downward facing position. The device may be raised or lowered into a cooling liquid. The device may be a standalone device, it may be in-line with a metal tube fabrication process, or it may be part of a furnace (e.g., a furnace bed), wherein the device may be used as part of a thermal treatment and then moved directly from the furnace into the cooling liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are flow charts illustrating an embodiment of a method of manufacturing a metal tube; and

FIG. 4A depicts an embodiment of a tiltable device with a metal tube immersed in a cooling liquid and positioned in a substantially horizontal position;

FIG. 4B depicts an embodiment of the tiltable device with the metal tube submerged in the cooling liquid and positioned in an elevated position; and

FIG. 4C depicts an embodiment of the tiltable device with the metal tube removed from the cooling liquid and positioned in a downward facing position.

DETAILED DESCRIPTION

Reference will now be made in detail to the accompanying drawings, which at least assist in illustrating various pertinent embodiments of the new technology provided for by the present disclosure

Referring now to FIG. 1, illustrated is one embodiment of a method for manufacturing a metal tube having an open end and an opposing closed end. The method comprises the steps of forming a hollow metal tube with one end open and one end closed 30, heat treating the metal tube 40, rapidly cooling the metal tube 50, and artificially aging or tempering the metal tube 90. These steps may facilitate consistent and/or more uniform cooling of the metal tube by releasing any evolved gases or vapors that develop during the immersing step.

The metal tube may be formed 30 using any conventional method for forming a hollow metal tube with one open end as described in the definitions section herein. After forming the metal tube 30, the method comprises heat treating 40 the formed metal tube to yield a heat treated metal tube. For instance, and referring to FIG. 2, heat treating the formed metal tube 40 may include solution heat treating 41. Solution heat treatment 41 involves the heating of an alloy to a suitable temperature, holding at that temperature for sufficient time to induce one or more of the constituents of the metal alloy to enter into solid solution, and then cooling rapidly (e.g. via cooling step 50) to hold these constituents in solution. Materials which respond to this process may include, for example, some aluminum alloys, titanium alloys, nickel alloys, cobalt alloys and steel alloys.

Referring now to FIGS. 2 and 3, after heat treatment 40, the heat treated metal tube is rapidly cooled 50 with a cooling liquid. Rapidly cooling 50 the heat treated metal tube may trap phases in solid solution. Rapidly cooling may comprise quenching in a quenching liquid or fluid, which restricts low-temperature processes, such as phase transformations, from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and kinetically accessible. The speed of quenching is important and may be varied to achieve certain desired properties in the metal (e.g. hardness, strength, microstructure, brittleness). Another factor to be considered in quenching is the work load and the ability of the quenching liquid to extract some heat from the metal tube at a sufficient rate to achieve the desired trapping of phases in solid solution.

As noted above, the quenching liquid may be either an aqueous liquid or an organic liquid or polymer, or a combination thereof. In some embodiments, the aqueous liquid is water, water plus carbon dioxide, or water plus a polymer. In another embodiment, the organic liquid comprises an oil or an organic aqueous polymer. The oil may be, for example, a straight oil, a water soluble oil, an oil-liquid emulsion, a synthetic oil, a semi-synthetic oil, or a microdispersion oil. The organic aqueous polymer may be, for example, a glycol polymer which may mixed with water, a polyalkylene glycol, a liquid water-soluble oxyalkylene polymer, a non-ionic water-soluble and water-dispersible polyvinylpyrrolidone or polyvinylcaprolactam copolymer, a non-ionic water-soluble or a water-dispersible polymer comprising a poly (oxyethyleneoxyalkylene) glycol polymer. In some circumstances, slow quenching is desirable as slow quenching may improve the metal tube's resistance to stress corrosion cracking of certain copper-free Al alloys, and may avoid cracking and or high residual stress in certain alloys such as steels.

Referring to FIG. 3, rapidly cooling 50 may further comprise the steps of immersing the heat treated metal tube in the cooling liquid 60, raising the open end of the tube to an elevated position 70, and lowering the open end of the tube to a downward facing position 80.

Immersing the metal tube 60 may comprise partially submerging the heat treated metal tube in the cooling liquid or fully submerging the heat treated metal tube in the cooling liquid. In another aspect, immersing 60 may comprise spraying cooling liquid on and/or in the heat treated metal tube through, e.g., the use of sprayers, nozzles or hoses. The immersing step 60 may further comprise positioning the metal tube 61, at least partially filling the metal tube with the cooling liquid 62 and developing an evolved gas inside the metal tube 63. In some embodiments, positioning 61 comprises positioning the metal tube in a substantially horizontal position prior to immersing. In some embodiments, positioning 61 comprises positioning the metal tube in the elevated position or the downward facing position prior to immersing 60.

Referring now to FIG. 3 and FIG. 4, the positioning step 61 may further comprise positioning the metal tube 10 on a tiltable device 30. The tiltable device 30 may be any device configured to retain the metal tube 10 while the tiltable device 30 and metal tube 10 are lowered into or raised from the cooling liquid 20. In some embodiments, the tiltable device 30 and the metal tube 10 may be submerged in the cooling liquid 20 with an open end 11 and a closed end 12 of the metal tube 10 being in a substantially horizontal position as seen in FIG. 4A. In some embodiments, as seen in FIG. 4B, the tiltable device 30 and the metal tube 10 may be fully submerged in the cooling liquid 20 with the metal tube 10 being in an elevated position and the open end 11 being in an upwards facing position. In some embodiments, the metal tube 10 may be in the elevated position before submersion. In some embodiments, the tiltable device 30 is capable of tilting the metal tube 10 such that the metal tube 10 can be transitioned between the substantially horizontal position, the elevated position, and a downward facing position. The tilting of the metal tube 10 allows for (1) releasing, via the open end 11 of the metal tube 10, an evolved gas that has developed within the metal tube 10, or within the closed end 12 of the metal tube 10, and (2) draining, via the open end 11, cooling liquid 20 from the metal tube 10. In some embodiments, the tiltable device 30 may be a quenching table. In some embodiments, both the heat treating step 40 and the rapidly cooling step 50 may be performed on the tiltable device 30. In some embodiments, the tiltable device 30 may be a bed of a furnace, wherein the bed may be dropped from the furnace into a cooling or quenching tank.

Still referring to FIG. 3 and FIG. 4, the raising step 70 may comprise releasing at least some of the evolved gas from the metal tube 71. To release the evolved gas 71, the metal tube 10 can be raised to the elevated position such that the open end 11 of the metal tube is in an upward facing position during or after the rapidly cooling step 50. In some embodiments, the raising step 70 comprises partially removing the metal tube 10 from the cooling liquid 20. In another embodiment, the raising step 70 comprises fully removing the metal tube 10 from the cooling liquid 20. Raising 70 the metal tube 10 may comprise raising the metal tube 10 to the elevated position while the metal tube 10 is immersed or submerged in the cooling liquid 20. Raising 70 the metal tube 12 may comprise raising the metal tube 10 to the elevated position after the metal tube 10 has been removed from the cooling liquid 20. In some embodiments, the raising step 70 comprises tilting the metal tube 10 such that the open end 11 faces upward by an angle of from 1 to 45 degrees above horizontal, or of from 5 to 25 degrees above horizontal, or of from 8 to 20 degrees above horizontal.

With the open end 11 of the metal tube 10 in the upwards facing position, some cooling liquid 20 may become trapped within the metal tube 10. Therefore, as demonstrated in FIG. 4C, it may be necessary to lower or tilt 80 the open end 11 of the metal tube 10 to the downward facing position, so that cooling liquid 20 may be drained 81 via the open end 11. In some embodiments, the lowering step 80 comprises tilting the metal tube 10 such that the open end 11 faces downward by an angle of from 1 to 45 degrees below horizontal, or of from 5 to 25 degrees below horizontal, or of from 8 to 20 degrees below horizontal.

Referring back to FIG. 1, after heat treatment 40 and rapidly cooling 50, additional aging of the extruded metal tube may be achieved (if so desired) either at room temperature (natural aging) or with an additional thermal aging step 90 (i.e. artificial aging or tempering). In some alloys, sufficient precipitation occurs in a few days at room temperature to yield stable products with properties that are adequate for many applications.

While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method of manufacturing a metal tube comprising: (a) heat treating a metal tube at an elevated temperature, wherein the metal tube comprises an open end and an opposing closed end; and (b) after the heat treating step, rapidly cooling the metal tube from the elevated temperature, wherein the rapidly cooling step comprises: (i) immersing the metal tube in a cooling liquid, wherein the immersing step comprises: (A) at least partially filling the metal tube with the cooling liquid; and (B) developing an evolved gas inside the metal tube; (ii) raising the open end of the metal tube to an elevated position, wherein the raising comprises releasing at least some of the evolved gas from the metal tube via the open end; and (iii) lowering the open end of the metal tube to a downward facing position, wherein the lowering comprises draining cooling liquid from the metal tube via the open end.
 2. The method of claim 1, wherein the metal tube is an extruded metal tube.
 3. The method of claim 1, wherein the metal tube is a machined metal tube, a casted metal tube, a hogged metal tube, or a metal tube fabricated from multiple parts.
 4. The method of claim 1, wherein the metal tube comprises a nickel alloy, a cobalt alloy, a steel alloy, an aluminum alloy or a titanium alloy.
 5. The method of claim 1, wherein the rapidly cooling step comprises quenching.
 6. The method of claim 1, wherein the cooling liquid is a quenching liquid.
 7. The method of claim 6, wherein the quenching liquid is an aqueous liquid or an organic liquid.
 8. The method of claim 7, wherein the aqueous liquid is water, water plus carbon dioxide, or water plus a polymer.
 9. The method of claim 7, wherein the organic liquid comprises an oil or an organic aqueous polymer.
 10. The method of claim 1, wherein the elevated temperature is sufficient to place soluble constituents of the metal into a solid solution and/or to affect or prevent a phase change in the metal.
 11. The method of claim 1, wherein the raising step (b)(ii) further comprises removing the metal tube fully from the cooling liquid.
 12. The method of claim 1, wherein the immersing step (b)(i) comprises: (A) submerging the metal tube in the cooling liquid; and (B) developing an evolved gas inside the metal tube.
 13. The method of claim 11, wherein the raising step (b)(ii) further comprises removing the metal tube fully from the cooling liquid.
 14. The method of claim 1, wherein the raising step comprises tilting the metal tube such that the open end of the metal tube faces upward by an angle of from 1 to 45 degrees above the horizontal axis, and wherein lowering step comprises tilting the metal tube such that the open end of the metal tube faces downward by an angle of from 1 to 45 degrees below the horizontal axis.
 15. The method of claim 1, wherein the immersing step (b)(i) comprises: (A) positioning the metal tube in a substantially horizontal position; (B) at least partially filling the metal tube with the cooling liquid; and (C) developing an evolved gas inside the metal tube.
 16. The method of claim 14, wherein the positioning step (A) comprises: positioning the metal tube in a substantially horizontal position on a tiltable device.
 17. The method of claim 16, wherein the tiltable device is a quenching table.
 18. The method of claim 1, wherein the immersing step (b)(i) comprises: (A) positioning the metal tube in a substantially horizontal position; (B) submerging the metal tube in the cooling liquid; and (C) developing an evolved gas inside the metal tube.
 19. The method of claim 18, wherein the raising step (b)(ii) further comprises removing the metal tube fully from the cooling liquid.
 20. A method of manufacturing a metal tube comprising: (a) heat treating an extruded metal tube at an elevated temperature, wherein the metal tube comprises an open end and an opposing closed end; and (b) after the heat treating step, quenching the metal tube, wherein the quenching comprises: (i) positioning the metal tube on a tiltable device; (ii) immersing the metal tube in a quenching liquid, wherein the immersing step comprises: (A) at least partially filling the metal tube with the quenching liquid; and (B) developing an evolved gas inside the metal tube; (ii) raising, with the tiltable device, the open end of the metal tube to an elevated position, wherein the raising comprises releasing at least some of the evolved gas from the metal tube via the open end; (iii) removing the metal tube and the tiltable device from the quenching fluid; and (iv) lowering, with the tiltable device, the open end of the metal tube to a downward facing position, wherein the lowering comprises draining cooling liquid from the metal tube via the open end. 